Role of Na⁺/Ca²⁺ Exchanger–Mediated Ca²⁺ Entry in Pressure-Induced Myogenic Constriction in Rat Posterior Cerebral Arteries

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The involvement of Ca²⁺ entry via the Na⁺/Ca²⁺ exchanger (NCX) in myogenic constriction of rat posterior cerebral arteries was investigated. RT-PCR identified mRNA for NCX1, 2, and 3 in the arteries. Na⁺ removal increased [Ca²⁺]_i, which was reduced by the NCX inhibitor SEA0400. SEA0400 inhibited the development, but not the steady-state, of pressure-induced myogenic constriction, whereas it decreased both the initial and sustained phases of [Ca²⁺]_i elevation. These results suggest that Ca²⁺ entry via NCX is involved in the development, but not the steady-state, of pressure-induced myogenic constriction.